Bioavailability of Micronutrients and Other Trace Elements in Soils

Home , Bioavailability (soil)

June 2016 Bulletin Number 894

H. Magdi Selim

Soil Aggregate

Cu Cd As

Trace Elements Trace Elements Mobility in soils Transport

Zn: 6 lb/A Zn: 0 lb/A

P2O5: 120 P2O5: 120

LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils 1 Table of Contents

INTRODUCTION 3 Frendlich Isotherm 3 Langmuir Isotherm 4

GENERAL TYPE ISOTHERMS 4 Empirical versus Mechanistic Models 4

EFFECT OF SOIL PROPERTIES 4 Soils and Experimental Methods 7 Adsorption Isotherms 9 Data Analysis 9

RESULTS AND DISCUSSION 9 Cadmium 9 Copper 10 Zinc 15 Nickel 16 Lead 16

PREDICTIONS 19

SUMMARY AND CONCLUSIONS 21

ACKNOWLEDGEMENTS 21 LITERATURE CITED 21

2 LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils INTRODUCTION Freundlich Isotherm Understanding trace element interactions in the The Freundlich isotherm is one of the simplest soil-water environment is essential in assessing their approaches for quantifying the behavior of retention of bioavailability and potential toxicity. Trace elements reactive solute with the matrix surfaces. It is one of the include several heavy metals, such as zinc (Zn), copper oldest nonlinear sorption equations and was based on (Cu), arsenic (As), cadmium (Cd) and vanadium (V), quantifying the solute adsorbed by unit mass of soil with among others. Several heavy metals such as Zn and Cu are increasing concentration which was described as essential micronutrients required in the growth of both b S = K f C (1) plants and animals. Micronutrients are often applied in the form of fertilizers or as supplements in animal feed. Heavy metals are extensively used as fungicides and as bactericides where S is the amount of solute retained by the soil in (mg -1 -1 in numerous pharmaceuticals. The bioavailability of trace Kg ), C is the solute concentration in solution (mg L ), is the partitioning coefficient (L kg-1) and the exponent elements in the soil-water environment depends on an Kf array of soil properties, including soil pH, organic matter b is dimensionless parameter. A major advantage of the (OM) content, amount and type of dominant clay and Freundlich approach is that it is capable of describing carbonates, among others. In addition, the counter ions successfully sorption for most trace elements, pesticides and other organics. The parameter represents the present in the soil system greatly influence the fate of trace Kf metals in soils. In fact, several studies suggested varied partitioning of a solute species between solid and liquid interactions of heavy metals with phosphates in soils. phases over the concentration range of interest and is analogous to the equilibrium constant for a chemical The adsorption of trace elements by clay minerals, metal reaction. oxides and organic materials has generally been explained This partitioning coefficient is a measure of the with two types of reaction mechanisms: (1) ion exchange Kf in the diffuse layer as a result of electrostatic force and affinity of a heavy metal to a soil and is widely reported in (2) surface complexation through the formation of strong the literature for various chemicals. The parameter b is a covalent bonds between heavy metal ions and specific measure of the extent of the heterogeneity of sorption sites reaction sites on surfaces of minerals or organic matters. on the soil having different affinities for solute retention by The ion exchange reaction is also referred to as nonspecific matrix surfaces. In a heterogeneous system, sorption by the sorption and the surface complexation is referred as specific highest energy sites takes place preferentially at the lowest sorption. solution concentrations, and as the sorbed concentration increases, successively lower energy sites become occupied. Adsorption isotherms or, more accurately, sorption This leads to a concentration-dependent sorption isotherms, are a convenient way to graphically represent equilibrium behavior, i.e., a nonlinear isotherm (Selim the amount of an adsorbed compound, or adsorbate, in 2015). When b equals unity, the Freundlich equation takes relation to its concentration in the equilibrium solution. on the form of the linear equation. In other words, an adsorption isotherm is a relationship relating the concentration of a solute on the surface of an S = Kd C (2) adsorbent to the concentration of the solute in the liquid phase at a constant temperature. Freundlich and Langmuir where Kd is the distribution coefficient (L/Kg). Asd K sorption equations are extensively used to describe sorption is used, this implies a linear, zero‑intercept relationship isotherms for a wide range of chemicals. Knowledge of between sorbed and solution concentration, which is sorption isotherms and adsorption phenomena is essential a convenient assumption but certainly not universally for understanding heavy solute retention and transport true. This linear model is often referred to as constant in soils and geological media. It is crucial for assessing the partition model and the parameter Kd value is a universally environmental risk of contamination or pollution caused accepted environment parameter that reflects the affinity by these elements. Studies on solute adsorption in soils of matrix surfaces for solute species. The Kd parameter are often conducted as a one component system, where the provides an estimate for potential adsorption of dissolved ions or molecules are treated individually, or they can be contaminants in contact with soil and is typically used in conducted as a multicomponent system, where the ions are fate and contaminant transport calculations. According subjected to competition among them. to the USEPA (1999), Kd is defined as the ratio of the contaminant concentration associated with the solid to the contaminant concentration in the surrounding aqueous solution when the system is at equilibrium.

LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils 3 Langmuir Isotherm L-curve isotherms. In L-type isotherms, at low solution concentrations, high-energy sites are occupied first. The Langmuir isotherm was developed to describe the Subsequently, as the concentration in solution increases, adsorption of gases by solids in which a finite number of sites of moderate and those of low affinities become adsorption sites in planer surfaces is assumed. The major occupied. The H-type isotherms are best characterized assumptions include that ions are adsorbed as a monolayer by extremely high sorption possibly due to irreversible on the surface, and the maximum adsorption occurs when reactions. The S-type isotherms indicate low affinity the surface is completely covered. Other assumptions are for sorption at low solution concentrations followed by that the surface considered is homogeneous, the sites are a gradual sorption increase. At a higher concentration, of identical adsorption energy or affinity over the entire sorption decreases, and sorption maxima are perhaps surface and that equilibrium is attained. As a result, a major attained. advantage of the Langmuir equation over the linear and Freundlich equations is that a maximum sorption capacity In the literature, L-type isotherms are frequently is incorporated into the formulation of the model, which encountered for most trace elements and heavy metals. may be regarded as a measure of the amount of available Specifically, Freundlich isotherms and Langmuir are retention sites on the solid phase. The standard form of the adopted for a wide range of solutes. C-type is often Langmuir equation is observed for pesticides (herbicides and insecticides) where S ω C linear isotherms are often observed. = (3) S max 1 + ω C Empirical versus Mechanistic Models where and Smax are adjustable parameters. Here (ml μg-1) is a measure of the bond strength of molecules on Fontes (2012) argued that the adsorption phenomenon can be represented by two main conceptual models: (1) the matrix surface, and Smax (μg g-1 of soil) is the maximum sorption capacity or total amount of available sites per unit the empirical, the ones initially derived from experiments, soil mass. and (2) the semiempirical or mechanistic, the ones that are based on reaction mechanisms. The main difference between these two models is the lack of an electrostatic GENERAL TYPE ISOTHERMS term in the empirical models whereas its presence is integral to mechanistic models. Mechanistic type models, Giles et al. (1974) proposed four general types of also known as chemical models, are expected to provide “a isotherms (C, L, H and S) which are illustrated in Fig. close representation of the real adsorption phenomenon 1. The C-type isotherms indicate partitioning of ions in the soil system” (Sparks 2003). Nevertheless, due to or molecules between the solution and sorbed phase as the complexity of chemical models, empirical models are in the linear model, equation (2). The L-type isotherm usually used in most solute studies with soils and geological is characterized by decreasing slopes as the vacant sites media. Moreover, empirical models have been widely used become occupied by the sorbed ion or molecule. Freundlich in soil science and environmental studies related to metals and Langmuir isotherm are commonly referred to as and anions adsorption and pesticide retention in soils. A listing of such models is presented in Table 1. These models do not take into consideration the electrostatic influence of the electrically charged surfaces in the solution or the influence of changes in surface charges due to the composition of soil solution. In the empirical model, the model form is chosen a posteriori from the observed adsorption data and to enable a satisfying fit of the experimental data the mathematical form and the number of parameters are chosen to be as simple as possible (Bradl, 2004).

EFFECT OF SOIL PROPERTIES Buchter et al. (1989) studied the retention of 15 elements by 11 soils from 10 soil orders to determine the Fig. 1. The four main types of isotherms (after Giles et al., effects of element and soil properties on the magnitude of 1974). the Freundlich parameters Kf and b. They also explored the

4 LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils Table 1. Selected equilibrium and kinetic type models for heavy metal retention in soils.

Model Formulation ‘ Equilibrium Type

Linear S = Kd C b Freundlich S = Kf C β General Freundlich S/Smax = [ω C/(1 + ωC)] n Rothmund-Kornfeld ion exchange Si/ST = KRK (Ci/CT)

Langmuir S/Smax = ω C/[1 + ωC]

General Langmuir Freundlich S/Smax = (ω C)β/[1 + (ωC)β]

Langmuir with Sigmoidicity S/Smax = ω C /[1 + ωC + σ/C] Kinetic Type

First-Order ∂S / ∂= t kfb (θρ / ) C − k S n n-th Order ∂S / ∂= t kfb (θρ / ) C − k S

Irreversible (sink/source) ∂S / ∂= t ksp (θρ / ) (CC − )

Second-order irreversible ∂S / ∂= t ks (θρ / ) C ( Smax − S)

Langmuir Kinetic ∂S / ∂= t kf (θρ / ) C ( Smax − S) − kb S Elovich ∂S / ∂= t Aexp ( −BS ) Power ∂S / ∂= t K (θρ / ) Cnm S Mass Transfer ∂S / ∂= t K (θρ / ) ( C − C*)

‘A, B, b, C*, Cp, K, Kd, KRK, kb, kf, ks, n, m, Smax, ω, β, and σ are adjustable model parameters, ρ is bulk density, Θ is volumetric soil water content, CT is total solute concentration and ST is total amount sorbed of all competing species.

Table 2. Taxonomic classification and selected chemical and physical properties of the soils used by Buchter et al.(1989)

Soil** Horizon Taxanomic Classification pH TOC sum of exch. MnO2 amor. free Al2O3 CaCO3 sand silt clay cations CEC OH Fe2O3 Fe2O3

% --cmolc/kg------%------% ------%------

Alligator Ap very-fine, m orillonitic, 4.8 1.54 30.2 3.5 0.028 0.33 0.74 0.15 ---- 5.9 39.4 54.7 acid, thermic Vertic Hap- laquept unnamed Ap Calciorthid 8.5 0.44 14.7 33.8 0.015 0.050 0.25 0.000 7.39 70.0 19.3 10.7 Cecil Ap clayey, kaolinitic, thermic 5.7 0.61 2.0 0.011 0.099 1.76 0.27 ------67.7 12.8 7,3 Typic Hapludult Cecil B clayey, kaolinitic, thermic 5.4 0.26 2.4 6.6 0.002 0.082 7.48 0.94 ---- 30.0 18.8 51.2 Typic Hapludult Kula Ap1 medial, isothermic 5.9 6.62 22.5 82.4 0.093 1.68 5.85 3.51 ---- 73.7 25.4 0.9 Typic Euthandept Kula Ap2 medial, isothermic 6.2 6.98 27.0 58.5 0.13 1.64 6.95 3.67 ---- 66.6 32.9 0.5 Typic Euthandept Lafitte Ap euic, thermic 3.9 11.6 26.9 4.7 0.009 1.19 1.16 0.28 ---- 60.7 21.7 17.6 Typic Medisaprist Molokai Ap clayey, kaolinitic, isohy- 6.0 1.67 11.0 7.2 0.76 0.19 12.4 0.91 ---- 25.7 46.2 28.2 per-thermic Typic Torrox Norwood Ap fine-silty, mixed (calc.), 6.9 0.21 4.1 0.0 0.008 0.061 0.30 0.016 ---- 79.2 18.1 2.8 thermic Typic Udifluvent Olivier Ap fine-silty, mixed, thermic 6.6 0.83 8.6 1.9 0.27 0.30 0.71 0.071 ---- 4.4 89.4 6.2 Aquic Fragiudalf unnamed B21h Spodosol 4.3 1.98 2.7 5.2 0.0000 0.009 0.008 0.22 ---- 90.2 6.0 3.8 Webster Ap fine-loamy, mixed, mesic 7.6 4.39 48.1 14.1 0.063 0.19 0.55 0.10 3.14 27.5 48.6 23.9 Typic Haplaquoll ** The states from which the soil samples originated are Louisiana (Alligator, Lafitte, Norwood and Olivier soils); South Carolina (Cecil soil); Hawaii (Kula and Molokai soils); Iowa (Webster soil); New Hampshire (Windsor soil); New Mexico (Calciorthid); and Florida (Spodosol).

LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils 5 Table 3. Freundlich model parameters Kf and b for of the soils used by Buchter et al. (1989) Element Initial Soil mean* species Alligator Calciorthid Cecil Kula Lafitte Molakai Norwood Olivier Oldsmar Webster Windsor

------Kf (mL/g) ------Co Co2+ 3.57E+01 2.51E+02 6.56E+00 1.05E+02 3.39E+01 9.25E+01 2.74E+01 6.70E+01 2.55E+00 3.63E+02 6.28E+00 3.75E+01 Ni Ni2+ 3.78E+01 2.06E+02 6.84E+00 1.10E+02 5.01E+01 4.49E+01 2.09E+01 5.05E+01 3.44E+00 3.37E+02 8.43E+00 3.61E+01 Cu Cu2+ 2.58E+02 2.62E+03 5.37E+01 2.05E+03 2.21E+02 3.68E+02 8.91E+01 2.18E+02 5.62E+01 6.35E+03 7.71E+01 3.17E+03 Zn Zn2+ 2.81E+01 4.20E+02 1.12E+01 2.38E+02 2.01E+01 8.04E+01 4.21E+01 8.91E+01 2.12E+00 7.74E+02 9.68E+00 4.79E+01 Cd Cd2+ 5.25E+01 2.88E+02 1.39E+01 1.87E+02 5.27E+01 9.12E+01 2.88E+01 9.79E+01 5.47E+00 7.55E+02 1.44E+01 5.93E+01 Hg Hg2+ 1.08E+02 1.96E+01 8.13E+01 2.49E+02 1.90E+02 1.20E+02 1.13E+02 1.29E+02 8.63E+01 2.99E+02 1.30E+02 1.15E+02 Pb Pb2+ 1.81E+03 2.36E+02 4.32E+07 9.18E+02 8.17E+03 3.85E+02 1.64E+04 1.36E+02 4.72E+02 3.37E+02 V VO-3 1.42E+02 1.08E+01 3.97E+01 2.22E+03 1.03E+02 5.05E+02 1.86E+01 9.12E+01 9.08E+01 8.07E+01 1.53E+01 1.03E+02

2- Cr CrO 4 3.41E+00 6.28E+01 3.03E+01 6.41E+00 5.47E+00 8.47E+00 1.12E+01 6- Mo Mo7O 24 5.75E+01 1.80E+01 4.11E+02 8.15E+01 1.18E+02 2.56E+01 4.38E+01 6.44E+01 3- As AsO 4 4.78E+01 8.87E+00 1.98E+01 1.50E+03 7.10E+01 1.56E+02 8.53E+00 4.60E+01 1.87E+01 2.36E+01 1.05E+02 4.71E+01 ------b ------Co Co2+ 0.953 0.546 0.745 0.878 1.009 0.621 0.627 0.584 0.811 0.782 0.741 0.754 Ni Ni2+ 0.939 0.504 0.688 0.738 0.903 0.720 0.661 0.646 0.836 0.748 0.741 0.739 Cu Cu2+ 0.544 1.140 0.546 1.016 0.987 0.516 0.471 0.495 0.602 1.420 0.567 0.755 Zn Zn2+ 1.011 0.510 0.724 0.724 0.891 0.675 0.515 0.625 0.962 0.697 0.792 0.739 Cd Cd2+ 0.902 0.568 0.768 0.721 0.850 0.773 0.668 0.658 0.840 0.569 0.782 0.736 Hg Hg2+ 0.741 0.313 0.564 1.700 0.751 0.960 0.582 1.122 0.513 2.158 0.681 1.008 Pb Pb2+ 0.853 0.662 5.385 0.558 1.678 0.741 0.998 0.743 0.743 1.485 - V VO 3 0.592 0.857 0.629 1.402 0.679 0.847 0.877 0.607 0.483 0.762 0.647 0.762 2- Cr CrO 4 0.504 0.609 0.374 0.607 0.394 0.521 0.501 6- Mo Mo7O 24 0.882 0.617 1.031 0.607 0.664 0.451 0.544 0.685 3- As AsO 4 0.636 0.554 0.618 1.462 0.747 0.561 0.510 0.548 0.797 0.648 0.601 0.698

correlation of the Freundlich parameters with selected soil CEC were significantly correlated to logK f values for cation properties and found that pH, cation-exchange capacity species. High pH and high CEC soils retained greater (CEC) and iron/aluminum oxide contents were the most quantities of the cation species than did low pH and low important factors for correlation with the partitioning CEC soils. A significant negative correlation between soil coefficients. The names, taxonomic classification and pH and the Freundlich parameter b was obtained for cation selected properties of the 11 soils used in their study are species whereas a significant positive correlation between listed in Table 2, and estimated values for Kf and b for soil pH and b for Cr(VI) was found (Buchter et al., 1989). selected heavy metals are given in Table 3. A wide range Greater quantities of anion species were retained by soils 7 -1 of Kf values from 0.0419 to 4.32x10 ml g were obtained, with high amounts of amorphous iron oxides, aluminum which illustrates the extent of heavy metals affinity among oxides and amorphous material than were retained by soils various soil types. Such a wide range of values was not with low amounts of these minerals. Several anion species obtained for the exponent parameter b, however. The were not retained by high pH soils. Despite the facts that magnitude of Kf and b was related to both soil and element element retention by soils is the result of many interacting properties. Strongly retained elements such as copper processes and that many factors influence retention, (Cu), mercury (Hg), lead (Pb) and vanadium (V) had significant relationships among retention parameters and the highest Kf values. The transition metal cations cobalt soil and element properties exist even among soils with

(Co) and nickel (Ni) had similar Kf and b values as did the greatly different characteristics. Buchter et al. (1989) made group IIB elements Zn and Cd. Oxyanion species tended the following conclusions: to have lower b values than did cation species. Soil pH and

6 LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils 1. pH is the most important soil property that affects A literature search revealed that sorption parameters as

Kf and b. affected by reaction time for a wide range of soils is lacking. In this bulletin, we presented results of trace elements 2. CEC influencesK for cation species. f retention of five trace elements by ten different soils. The 3. The amounts of amorphous iron oxides, aluminum soils varied extensively, and the trace elements were Cu, Zn, oxides and amorphous material in soils influence Pb, Ni and Cd. The selection of these heavy metals was both cation and anion retention parameters. made based on EPA Code of Federal Regulation CFR 40 Part 503 for land-applied sewage sludges (USEPA, 1993, 4. Except for Cu and Hg, transition metals (Co and 1994a, 1994b, 1995). The specific objectives were twofold: Ni) and group lIB cations (Zn and Cd) have similar first, to quantify heavy metal affinity for the different soils, K and b values for a given soil. f and second, to quantify the effect of time of reaction or 5. Significant relationships between soil properties kinetics on heavy metals affinities. A third objective was and retention parameters exist even in a group of to assess the capability of Buchter et al. (1989) models in soils with greatly different characteristics. predicting measured data.

The relationships between soil properties and retention Soils and Experimental Methods parameters (e.g., Fig. 2) can be used to estimate retention parameters when the data for a particular element and soil The names, taxonomic classifications and selected type are lacking but soil property data are available. For properties of the 10 soils used in this study are listed in example, the retention characteristics of Co, Ni, Zn and Cd Table 4. The Ap horizons of all soils were used in this are sufficiently similar that these elements can be grouped retention study. The only exception is that for the sandy together, and an estimated b value for anyone of them candor subsurface sample which was sampled at a depth could be estimated from soil pH data using the regression of 90 cm. Physical and chemical properties of the 10 soils equation for curve A in Fig. 2. For many purposes such an are given in Table 5. Soil pH was measured using a one- to-one soil/water suspension, and the at pH 7 estimate would be useful, at least as a first approximation, NH4OAc in describing the retention characteristics of a soil. method was used to determine cation exchange capacity (CEC). Total carbon was measured using a dry combustion Curve A: b = 1.24 - 0.0831 pH (r = 0.83) (4) method (Elementar Americans Inc., Mount Laurel, NJ). Curve B: b = -0.0846 + 0.116 pH (r = 0.98) (5) The carbonate content of soil was determined according to the pressure calcimeter method. For the batch experiments, a 5-mL aliquot was sampled and the total Cd, Cu, Ni, Pb

Fig. 2. Correlation between soil pH and Freundlich parameter b (after Buchter et al. 1989). Curve A is a regression line for Co, Ni, Zn, and Cd (b = 1.24 - 0.0831 pH, r = 0.83). Curve B is for Cr(VI) (b = -0.0846 + 0.116 pH, r = 0.98).

LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils 7 Table 4. Selected soil properties of the 10 soils used in the study.

Soil Series State Texture pH %C CEC Sand Silt Clay Carbonates % % % (%) Arapahoe NC FSL 5.02 10.22 30.10 64.7 25.2 10.1

Candor - Surface NC LCoS 4.39 2.24 5.30 84.1 6.6 9.3

Candor - NC CoS 4.05 0.56 1.70 91.0 4.1 4.9 Subsurface Olney CO FSL 8.12 1.14 10.10 71.1 11.6 17.3 3.32

Lincoln OK VFSL 7.54 1.27 3.00 59.5 29.7 10.8 3.6

Nada TX FSL 6.61 0.76 6.30 56.8 33.6 9.6

Morey TX L 7.74 1.05 27.80 29.4 46.5 24.1

Crowley LA SiL 5.22 1.16 16.50 8.3 77.3 14.4

Sharkey LA SiC 5.49 2.76 39.70 6.4 48.6 45.0

Houston TX SiC 7.78 4.26 47.70 9.6 41.2 49.2 26.0

Table 5. Taxonomic classification of the 10 soils used in this study. Soil Series State Taxonomic Classification Arapahoe NC Coarse-loamy, mixed, semiactive, nonacid, thermic Typic Humaquepts

Candor - Surface NC Sandy, kaolinitic, thermic Grossarenic Kandiudults

Candor - Subsurface NC Sandy, kaolinitic, thermic Grossarenic Kandiudults

Olney CO Fine-loamy, mixed, superactive, mesic Ustic Haplargids Lincoln OK Sandy, mixed, thermic Typic Ustifluvents Nada TX Fine-loamy, siliceous, active, hyperthermic Albaquic Hapludalfs

Morey TX Fine-silty, siliceous, superactive, hyperthermic Oxyaquic Argiudolls

Crowley LA Fine, smectitic, thermic Typic Albaqualfs

Sharkey LA Fine-silty, mixed, active, thermic Typic Glossaqualfs

Houston TX Fine, smectitic, thermic Udic Haplusterts

8 LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils and Zn concentration in the supernatant solution were RESULTS AND DISCUSSION analyzed using inductively coupled plasma-atomic emission spectrometry (ICP-AES) (Spectro Citros CCD, Spectro Results of the retention of the five heavy metals by the Analytical Instruments, Kleve, Germany). different soils are presented as adsorption isotherms. This is a convenient way to graphically represent the amount

Adsorption Isotherms of an adsorbed element in relation to its concentration in solution. There are several ways to present the different To assess the retention capability of the different soils isotherms. In this study, for each heavy metal, we present used in this study to retain heavy metals, adsorption isotherms for all soils. An alternative way is to present, isotherms were measured. The batch equilibration for each soil, isotherms for the five heavy metals. Although technique was with four different initial concentrations we selected to present isotherms for each heavy metal of the heavy metals. Due to the anticipated differences separately, common features among the different soils in the affinity of the heavy metals to soils, the range of are highlighted throughout the discussion. As clearly initial concentrations used varied based on the heavy illustrated in the following sections, retention of all five metal. For lead (Pb) maximum input concentration heavy metals was significantly influenced by soil pH, CEC, used was 400 mg/L whereas for all other heavy metals organic matter and carbonate content. Generally, soils the maximum concentration used varied from 100-150 with lowest pH and CEC exhibited lowest retention. In mg/L. All solutions were prepared in 0.005 M Ca(NO3)2 contrast, soils with high CEC and high pH due to the as a background solution. Adsorption was performed in presence of carbonates showed high affinity for all heavy duplicates where 3-g sample of each soil were placed in metals. Teflon centrifuge tubes and mixed with 30 mL solution of known heavy metal concentrations described above. The Cadmium tubes were sealed, and the mixtures were continuously shaken for 24 hours and then centrifuged for 10 minutes. Cadmium adsorption isotherms for all 10 soils A 5-mL aliquot was sampled, and the concentration of are presented in Fig. 3. The results shown illustrate the the heavy metal in the supernatant at reaction times of 1 differences in the amount of Cd retained by the different and 7 days was measured. The mixtures were subsequently soils. This is indicated by Cd concentration in the soil returned to the shaker after each sampling. The collected solution that did not exceed 18 mg/L for Sharkey, samples were analyzed using ICP–AES. The detection Arapahoe and Houston black clay. In contrast, for Lincoln, limits of ICP-AES were 2.3, 3.6, 10.0, 28.0 and 1.2 for Cd, Nada and the Candor sand, Cd concentrations in soil Cu, Ni, Pb and Zn μg/L (ppb) respectively. The amount solution exceeded 50 mg/L. Lower concentration indicates of a heavy metal retained (sorbed) by the soil matrix was stronger retention by the soil. Soils high in clay content determined by the difference between the concentrations of and organic matter soils exhibited highest retention for Cd. the supernatant and that of the initial solutions. In contrast, Candor sands and high pH soils Lincoln and Nada showed least retention for Cd.

Data Analysis All Cd isotherms in Fig. 3 are strongly nonlinear with varying degree of sorption among soils. The solid and The linear and Freundlich models, equations (1) and dashed curves shown represent calculations based on the (2), were fit to the isotherm data using a nonlinear, least- Freundlich, equation (1). Parameter values for Kd of the squares curve-fitting method. The curve-fitting method is linear model and Kf and b for the Freundlich model along basically the maximum neighborhood method and is based with their r2 and RMSE statistics are given in Table 6. on an optimum interpolation between the Taylor series Based on these statistics, the use of a linear model is not method and the method of steepest descent. Criteria used recommended. In Table 7, Freundlich parameter Kf and for estimating goodness-of-fit of the model to the data were b estimates for all 10 soils are presented. The range of b the coefficient of determinationr ( 2) and the root mean values was 0.35 to 1.0 where highest values of 0.84, 0.94 square statistics (RMSE), and 1.0 were for Candor surface and subsurface sands and the high pH Lincoln soil. Krishnamurti and Naidu rss (5) RMSE = (2003) reported nonlinear sorption for two soils having − NPd pH > 8. Buchter et al. (1989) reported a range of 0.56 to 0.96, which is consistent with the results presented here. where rss is the residual sum of squares, N is the number d Recently, Elbana and Selim (2010) estimated b values of of data points and P is the number of fitted parameters. 0.28 for a calcareous soil and 0.46 for an acidic soil.

LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils 9 1600 The nonlinearity of Cd isotherms shown in Fig. 3 Morey have significant implications. First, a wide range of 1400 Olney concentrations is critical to obtain accurate information 1200 on the affinity of Cd at different concentration levels. 1000 Specifically, the use of a single point isotherm, which Crowley 800 is often reported in the literature, assumes a linear

600 isotherm and leads to erroneous values of the affinity coefficient. Second, the concentration level chosen may 400 result in overestimation of the affinity coefficient. At low Cd sorbed (mg/kg) 200 Cd isotherms concentrations, high affinities are encountered, which 0 results in high affinity coefficients. The use of such affinity 0 10 20 30 40 50 coefficients would result in erroneous estimated and should Cd in solution (mg/L) not be used at higher concentrations. It should also be pointed out that the due to the nonlinearity of sorption isotherms, Cd affinity decreases as the concentration 1600 increased and thus is more susceptible to greater mobility Morey 1400 Olney in the soil. 1200 Cadmium exhibited kinetic behavior for all soils where 1000 increased Cd sorption was measured over time. This is Crowley 800 illustrated by the selected isotherms in Fig. 4 for Houston

600 and Arapaho. Strong time-dependent sorption was observed for Houston soil, whereas Arapaho exhibited 400 limited kinetic behavior. High pH soils such as Lincoln and Cd sorbed (mg/kg) 200 Cd isotherms Olney exhibited moderate kinetic behavior, whereas limited 0 kinetics was observed for the remaining soils. Increases in 0 10 20 30 40 50 Kf due to time of reaction are given in Table 7. In addition, Cd in solution (mg/L) the parameter b did not change with time for all soils. This is an important finding in predictions of retention and mobility of Cd in soils where only b is considered time 1000 invariant. Evidence of time-dependent sorption in soils has Cd isotherms been observed by numerous investigations (e.g., Aringhieri 800 Nada et al., 1985; Selim et al. 1992). Hinz and Selim (1994) Lincoln Candor- Surface observed limited Cd kinetic behavior for acidic soils. 600 Copper Copper isotherms for the selected soils are shown in Fig. 400 5. The isotherms are highly nonlinear with varying degrees Candor- of sorption among soils. Parameter values for Kd of the Cd sorbed (mg/kg) sorbed Cd 200 Subsurface linear model and Kf and b for the linear and Freundlich models are given in Table 6. Copper affinity for Arapaho 0 soil with high OM exceeded that for all soils shown in 0 20 40 60 80 100 120 Fig. 5. The only exception was for Houston black clay Cd in solution (mg/L) where Cu was retained entirely (>99%) with measured Cu concentrations in soil solution less < 0.1 mg/L (figure not shown). Such strong Cu sorption is indicative of irreversible retention and possibly precipitation. In Fig. 3. Cadmium isotherms for several soils after 1 day of contrast, Candor sands exhibited least amount of retention reaction. Solid and dashed curves are simulations using the Freundlich model. of Cu (figure not shown). Based on Table 6, the Freundlich parameter b ranged from 0.29 to 1.32 with b > 1 only for the alkaline pH soils, namely, Houston Black clay and Morey and Lincoln soils. Elbana and Selim (2011) estimates b values of 0.23 for an acidic soil and 1.25 for a calcareous soil. They also reported their calcareous soil exhibited an order of magnitude greater Cu sorption when

10 LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils Table 6. Linear and Freundlich adsorption parameters for cadmium (Cd) after a 1-day reaction time for all soils.

2 2 Soil Series Kd r Kf b r (mL/g) (mL/g) Arapahoe 144.680 0.920 313.180 0.650 0.998 Candor-surface 6.820 0.989 13.620 0.840 0.999 Candor-subsurface 5.210 0.998 6.304 0.957 0.999 Olney 42.343 0.645 367.210 0.352 1.000 Lincoln 13.091 0.703 157.040 0.392 0.998 Nada 9.691 0.878 92.939 0.465 0.999 Morey 56.666 0.809 267.606 0.494 0.999 Crowley 26.684 0.932 93.422 0.653 0.999 Sharkey 87.844 0.927 220.879 0.651 0.999 Houston 380.021 0.810 738.244 0.499 0.998

Table 7. Freundlich model Kf and b parameter values for 10 soils and five heavy metals.

Element Arapahoe Candor- Candor- Olney Lincoln Nada Morey Crowley Sharkey Houston Surface Subsurface

Kf - 1 day Cu 1004.91 64.51 16.15 5027.78 512.40 235.45 833.78 213.88 501.73 66205.54 Zn 150.51 CS 0.0038 552.83 181.27 60.29 323.29 37.21 91.07 988.81 Cd 313.18 13.62 6.30 367.21 157.04 92.94 267.61 93.42 220.88 738.24 Ni 78.51 CS 0.0008 169.79 64.04 16.65 159.24 17.72 65.92 373.10 Pb 3792.51 93.99 7.09 5169.46 1679.58 1360.44 4224.09 1280.45 2825.04 C S*

Kf - 7 day Cu 1305.73 103.12 72.88 2209492.85 3993.56 350.52 4842.30 283.91 630.16 29606459.71 Zn 22.37 0.51 1.53 847.56 243.53 50.98 387.64 45.00 96.24 1258.36 Cd 323.09 16.68 7.94 514.97 0.39 93.58 301.51 103.19 224.12 935.35 Ni 89.39 CS 0.0006 261.10 134.28 28.04 130.48 23.51 70.94 467.14 Pb 4705.95 174.11 33.53 6889.88 3863.83 1497.59 5296.20 1452.22 3275.69 C S*

b - 1 day Cu 0.54 0.40 0.54 1.32 0.29 0.30 0.41 0.41 0.46 1.16 Zn 0.43 2.85 2.50 0.31 0.32 0.51 0.37 0.66 0.70 0.33 Cd 0.65 0.84 0.96 0.35 1.00 0.47 0.49 0.65 0.65 0.50 Ni 0.73 CS 2.74 0.56 0.56 0.85 0.60 0.90 0.84 0.54 Pb 0.62 0.65 0.95 0.16 0.18 0.18 0.08 0.28 0.27 C S

b - 7 day Cu 0.58 0.39 0.34 3.96 1.10 0.22 0.96 0.35 0.44 3.48 Zn 0.83 1.32 1.14 0.37 0.33 0.56 0.34 0.62 0.69 0.28 Cd 0.66 0.80 0.92 0.30 0.33 0.48 0.46 0.63 0.65 0.54 Ni 0.74 CS 2.83 0.62 0.57 0.73 0.65 0.83 0.84 0.64 Pb 0.69 0.56 0.70 0.24 0.36 0.18 0.12 0.26 0.29 C S * CS = Complete sorption.

LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils 11 Houston Black clay extensive time-dependent sorption was 1800 observed. In Table 6, the respective values of Kf and b for 1600 Houston 1-day sorption are presented. In addition, the parameter b 1400 did not change with time for acidic soils, whereas for high 1200 pH soils (>6.6) increased values for b was observed. Selim and Ma (2001) reported no change of over time for one 1000 b acidic soil. 800

600 The observed increase of Cu sorption over time 1 d illustrated in figs. 6 and 7 has significant implications. 400 Most significant is that and parameters based on 1- Cd sorbed (mg/kg) 7 d Kf Kd 200 Freundlich and 7-day reaction time represent an underestimation of 0 the extent of sorption of heavy metals in soils. Therefore, 0 1 2 3 4 5 prediction of the extent of affinity and potential mobility Cd in solution (mg/L) of a heavy metal, based on 1-day sorption data, is likely to provide erroneous results and thus is not recommended.

1600 Arapahoe 1400 1200 1200 Arapahoe 1000 Sharkey 1000 Morey 800 800

600 600 Lincoln 400 1 d 400

Cd sorbed (mg/kg) 7 d 200 Freundlich

0 Cu sorbed (mg/kg) 200 0 2 4 6 8 10 12 Cu Isotherms 0 Cd in solution (mg/L) 0 1 2 3 4 5 6

Fig. 4. Cadmium isotherms for Morey and Lincoln soils after Cu in solution (mg/L) 1 and 7 days of reaction. Curves are simulations using the Freundlich model. 800 compared to an acidic soil. Nonlinear isotherms having b > Crowley 1 are not commonly encountered for acidic soils, however. 600 Moreover, such nonlinearity (b>1) is often indicative of Nada precipitation as the dominant retention mechanism (Selim, 2014). 400 Several scientists, including Florido et al. (2010), Wang et al. (2009) and Lopez-Periago et al. (2008) reported 200

time-dependent retention of Cu in several soils. Lopez- Cu sorbed (mg/kg) Periago et al. (2008) studied adsorption and release Cu Isotherms kinetics by several acidic soils where hysteretic behavior 0 was dominant for several soils. In this study, Cu exhibited 0 5 10 15 20 25 30 kinetic behavior for all soils where Cu sorption increased Cu in solution (mg/L) from 1 to 7 days. This is illustrated by the selected isotherms in figs. 6 and 7 for Houston and Crowley soils. Our results indicated the acidic soils such as Sharkey, Arapaho, Candor sands and Nada exhibited least kinetics. Fig. 5. Copper isotherms for different soils after 1 day of In contrast, high pH soils, e.g., Morey, Lincoln and reaction. Solid curves are simulations using the Freundlich model.

12 LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils 1000 1200 Sharkey soill Morey soil 800 1000

800 600

600 400 400 1 d 1 d 200 7 d

Cu sorbed (mg/kg) 7 d Freundlich Cu sorbed (mg/kg) 200 Freundlich 0 0 0 1 2 3 4 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Cu in solution (mg/L) Cu in solution (mg/L)

1000 Crowley 1000 800 Lincoln soil 800 600

400 600

1 d 200 400

Cu sorbed (mg/kg) 7 d Freundlich 1 d 200 0 Cu sorbed (mg/kg) 7 d 0 5 10 15 20 25 Freundlich Cu in solution (mg/L) 0 0 1 2 3 4 5 6 Fig. 6. Copper isotherms for Sharkey and Crowley soils after Cu in solution (mg/L) 1 and 7 days of reaction. Curves are simulations using the Freundlich model. Fig. 7. Copper isotherms for Morey and Lincoln soils after 1 and 7 days of reaction. Curves are simulations using the Freundlich models.

LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils 13 2000 Houston 1600 Onley Morey 1200

Sharkey 800 Zn SorbedZn (mg/Kg) 400

Zn - Isotherms 0 0 10 20 30 40 Zn Concentration (mg/L)

1000 Arapahoe

800 Lincoln Crowley 600 Nada

400 Zn SorbedZn (mg/Kg) 200 Zn - isotherms 0 0 20 40 60 80 100 Zn Concentration (mg/L)

Fig. 8. Zinc isotherms for four soils after 1 day of reaction. Solid and dashed curves are simulations using the Freundlich model.

14 LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils Zinc 1200 Zinc isotherms for selected soils are shown in Fig. 8. These Sharkey results indicate much less affinity for Zn by all 10 soils when 1000 compared to copper. Houston soil exhibited highest sorption, whereas most loamy soils indicated moderate sorption for 800 zinc. For Candor sand soils, extremely low sorption for Zn was observed (figure not shown). For all soils, Zn isotherms 600 were nonlinear, and the Freundlich, equation (1), provided good description of the results. The parameter b is a measure 400 of the heterogeneity of sorption sites, where sorption by the 1 d highest energy sites takes place preferentially at the lowest SorbedZn (mg/Kg) 200 7 d solution concentrations, and as the sorbed concentration Freunlich increases, successively lower energy sites become occupied. 0 This leads to a concentration-dependent sorption equilibrium 0 10 20 30 40 behavior, i.e. nonlinear isotherm (Selim, 2014). The results Zn Concentration (mg/L) for the Freundlich parameter b values given in Table 7 indicate a wide range of values from 0.31-0.70. The only exception was Candor surface and subsurface sands with b values > 2.5 where least affinity for Zn was observed. Zhao and Selim 1600 Houston (2010) reported a range of b values for Zn from 0.40-0.50 for one neutral and two acidic soils. Buchter et al. (1989) 1200 reported a range of b values of 0.51 to 1.01 with the highest b for a calcareous soil. A comparison of various isotherms indicate that Cu is 800 adsorbed more strongly than Zn as well as Cd. In recent years, 1 d

some authors have examined metal competition in various SorbedZn (mg/Kg) 400 7 d types of soils. Based on their results, copper is adsorbed more Freundlich strongly than Zn and Cd in calcareous soils (Mesquita and Vieira e Silva, 1996); acid soils (Agbenin and Olojo, 2004; 0 0 1 2 3 4 5 Arias et al., 2006); clay minerals; and isolated organic soil Zn Concentration (mg/L) components (Saha et al., 2002). Zinc isotherms for selected soils after 1- and 7-day adsorption are shown in Fig. 9. These isotherms show the 1600 influence of time of adsorption varied extensively among soils. Olney In fact, for soils that exhibited strong sorption, increased sorption from 1-7 days was much greater than all other soils. 1200 This is illustrated by the lack of time-dependent behavior for sorption by Sharkey when compared to Houston soil. In addition, the parameter b did not change with time for 800 all soils. The observed limited kinetics for Sharkey soil is an indication of fast sorption processes possibly dominated by 1 d

Zn SorbedZn (mg/Kg) 400 ion exchange. On the other hand, it is likely that irreversible 7 d sorption due to the presence of carbonates resulted in the Freundlich observed strong kinetic behavior for Houston soil. Kinetic 0 retention behavior of Zn has been observed by several 0 2 4 6 8 10 12 14 16 18 20 investigators (Dang et al.,1994; Perez-Novo; 2011). Kinetic Zn Concentration (mg/L) behavior also may be deduced from the slow release during Zn transport as exhibited by extensive tailing of breakthrough curves (Voegelin et al., 2001; Voegelin et al., 2005). Recent evidence of Zn kinetics during Zn release or desorption in acidic and neutral soils was reported by Perez-Novo et al. Fig. 9. Zinc isotherms for Sharkey, Houston and Olney soils (2011b) and Zhao and Selim (2010). after 1 and 7 days of reaction. Curves are simulations using the Freundlich model.

LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils 15 Nickel 1400 Nickel isotherms for selected soils are shown in Fig. Houston Olney 1200 10. Results from this study indicate that Houston soil Morey Sharkey exhibited highest sorption, whereas most loamy soils 1000 indicated less Ni sorption. Among all soils, Candor sands 800 exhibited the lowest affinity for nickel (data not shown). The Freundlich parameterb given in Table 7 ranged from 600 Arapahoe 0.54 to 0.90 except for Candor surface and subsurface 400 sands with b >1. Buchter et al. (1989) reported a range of (mg/Kg) Sorbed Ni 0.51 to 0.90 including that for a calcareous soil. Lixia and 200 Selim (2010) reported a range of b values from 0.49-0.59 Ni - Isothorms for one neutral and two acidic soils. 0 0 10 20 30 A number of studies suggested that Ni may be Ni Concentration (mg/L) considered as a weakly sorbed heavy metal when compared to others such as Pb, Cu and Zn (Tiller et. al, 1984; 800 Atanassova, 1999). Specifically, Ni was observed to have Lincoln low affinity for reactive phases in acidic soils. This finding is Crowley consistent with our results, and Ni can thus be considered 600 mobile and susceptible to transport. In fact, Atanassova (1999) argues that Ni and Cd are two cations that have low Nada affinities for soil colloids and are generally considered to be 400 weakly bonded metals. Our results are consistent with the above findings, and Ni has the least affinity to soils among Ni Sorbed (mg/Kg) 200 all five heavy metals investigated.

Time-dependent Ni sorption is illustrated by the Ni - Isotherms isotherms shown in figs. 11 and 12. The extent of kinetics 0 is manifested by the increased amount of sorption after 0 20 40 60 80 7 days compared to 1 day. The influence of kinetics was Ni Concentration (mg/L) greatest for Houston and Olney (Fig. 11) and least for Fig. 10. Nickel isotherms for several soils after 1 day of Arapahoe and Sharkey soils (Fig. 12). The extent of reaction. Solid and dashed curves are simulations using kinetics varied among other soils where a limited increase the Freundlich model. in sorption over time was observed for acidic soils and consistent with our findings for Zn as discussed above. This is manifested by theK values for 1 and 7 days f Lead presented in Table 7. In addition, the parameter b did not change with time for all 10 soils. Lixia and Selim (2010) It is well accepted that Pb is one of the heavy metals reported that for one neutral and two acidic soils there was with a strong affinity to soils. In fact, Pb is often regarded no change of b with time of reaction up to 22 days. as immobile due to its high sorption and slow release from soils (Kabata-Pendias and Sadueski, 2007). The extent Information on the rate of sorption of Ni on soils is of Pb mobility in soils is controlled by soil characteristics limited, where in most studies equilibrium conditions and environmental conditions. Soil pH, CEC, clay are assumed. A limited number of studies, however, have content, CaCO3 and OM were positively correlated with investigated release or desorption of Ni from minerals Pb sorption in soil (Hooda and Alloway, 1998). This is and soils (Atanassova, 1999, Scheckel and Sparks, 2001, supported with various studies; for example, Martínez- Barrow et al., 1989). Antnassova (1999) reported that most Villegas et al. (2004) that showed that Pb sorption Ni sorbed by a Dutch soil in a 24-hour equilibrium batch isotherms were strongly nonlinear, and the sorption experiment could be released by excess of calcium and only capacity increased with increasing pH. Strawn and Sparks a small proportion of Ni was specifically sorbed. Vega et al. (2000) found that removing OM decreased Pb sorption by (2006) reported that no significant amount of heavy metals 40% compared with untreated soil. Moreover, McKenzie (Pb, Zn, Cu and Ni) was desorbed from mine soils. (1980) found that Pb sorption by Mn oxides was up to 40 times greater than that by Fe oxides, and no evidence for oxidation of Pb or the formation of specific Pb–Mn

16 LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils 1500 1200 Houston Sharkey 1000 1200

800 900 600

600 400 Ni Sorbed (mg/Kg) Ni Sorbed (mg/Kg) 300 1 d 1 d 200 7 d 7 d Freundlich Freundlich 0 0 0 2 4 6 8 10 0 5 10 15 20 25 30 Ni Concentration (mg/L) Ni Concentration (mg/L)

1500 1200 Olney Arapahoe 1000 1200

800 900 600

600 400 Ni Sorbed (mg/Kg) Ni Sorbed (mg/Kg) 300 1 d 200 1 d 7 d 7 d Freundlich Freundlich 0 0 0 5 10 15 20 25 30 0 10 20 30 40 Ni Concentration (mg/L) Ni Concentration (mg/L)

Fig. 11. Nickel isotherms for Houston and Olney soils after 1 and Fig. 12. Nickel isotherms for Sharkey and Arapahoe soils 7 days of reaction. Curves are simulations using the Freundlich after 1 and 7 days of reaction. Curves are simulations using models. the Freundlich modes.

minerals was found. Lead isotherms for all soils are extent of retention over 7 days for Morey and Candor shown in Fig. 13. Isotherm results indicate a wide range surface sand. With the exception of Lincoln soil, all others of affinities for Pb in these soils. Houston soil exhibited exhibited less kinetics than those presented in Fig. 14. highest sorption in which lead concentration in the soil Therefore, the rate of Pb sorption is fast in which quasi solution was below detection (28 μg/L) for the entire range equilibrium is likely reached in a few hours or days. of input concentrations. All other soils exhibited different Moreover, the parameter b did not change with time for all degrees of affinities for lead as illustrated in Fig. 13. Soils 10 soils. with high OM content, such as Arapahoe, as well as soils with high clay contents, such as Sharkey, exhibited high sorption in which Pb concentration was less than 3.1 mg/L. As expected, Pb retention was lowest in Candor sands with increasing Pb sorption for Nada, Lincoln and Crowley soils. It should also be emphasized that Olney soil with high pH and carbonate content exhibited high sorption for lead. Due to the high affinity of Pb to soils, sorption was rapid with little additional sorption of 1 day of reaction. The isotherms shown in Fig. 14 illustrate the

LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils 17 4000 4000 Crowley Pb - Isotherms Lincoln

3000 Nada 3000 Morey

2000 2000 Candor Surface

Pb Sorbed (mg/Kg) Pb Sorbed 1000 Pb Sorbed (mg/Kg) Sorbed Pb 1000 1 d Candor Subsurface 7 d Freundlich 0 0 50 100 150 200 0 0.00 0.05 0.10 0.15 0.20 0.25 Pb Concentration (mg/L) Pb Concentration (mg/L)

2500 4000 Houston Candor - Surface Morey 2000 3000

Olney 1500

2000 1000 Pb Sorbed (mg/Kg) Sorbed Pb

Pb Sorbed (mg/Kg) Sorbed Pb 1 d 1000 500 7 d Freundlich Pb - Isotherms 0 0 0 20 40 60 80 100 120 0.00 0.04 0.08 0.12 0.16 0.20 Pb Concentration (mg/L) Pb Concentration (mg/L) Fig. 14. Lead isotherms for Morey and Candor-surface soils 5000 after 1 and 7 days of reaction. Curves are simulations using the Freundlich models. Arapahoe Sharkey 4000

3000

2000 PbSorbed (mg/Kg) 1000 Pb - isotherm 0 0 1 2 3 Pb Concentration (mg/L)

Fig. 13. Lead isotherms for several soils after 1 day of reaction. Curves are simulations using the Freundlich models.

18 LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils PREDICTIONS here that b values for all soil were included in the regression analysis except for the two sandy Candor soils. In the A correlation of Kf and b values with soil properties soils, due to possible precipitation, b values for most heavy was carried out for all heavy metals in a similar manner metals were > 1 and were thus excluded. to that of Buchter et al. (1989). Here we used parameter values obtained after a 1-day reaction. We found highest We also performed regression analysis based on correlation with pH followed by organic matter. As parameters after 7 days of reaction in find out whether b indicated in Fig. 15, considerable scatter with and a general values from 1 day was significantly different from 7-day trend for a decreasing b as pH increased was observed. results (Fig. 16). The regression equation for 7 days is Linear regression of b versus pH for individual heavy b=1.115 - 0.0908 pH R=0.537 (7) metals and found that Cd and Pb best coefficients of A comparison of the two regression equations (6) and correlation (r = 0.809 and 0.774, respectively). In the (7) for 1 and 7 days indicates different intercepts. Values meantime, values of b for Cd did not display specific patter for the slope, however, were almost identical (0.0900 and with increasing pH and was thus excluded from further 0.908) for 1 and 7 days. Additionally, a paired t-test for the analysis. As a result, the regression (solid) line shown in significance betweenb parameter values based on 1 and 7 Fig. 15 represents overall regression for the four heavy days revealed no significance between the two data sets (p metals (zinc, lead, cadmium and nickel). The following = 0.773, t = - 0.290). This finding, that b is time invariant, regression equation was obtained for a 1-day reaction has a significant implication since it simplifies predictive capability predictive capabilities of affinity for sorption of b =1.087 - 0.0900 pH R=0.503 (6) heavy metals with time. Such information is important in The dashed line shown in the Fig. 15 is based on estimation of the bioavailability and risk assessments of the equation (4) of Buchter et al. (1989). Although the dashed potential mobility of these trace elements for a wide range overestimated most b values, the slope of the dashed and of soils. solid lines were similar, i.e., parallel. We should emphasis

1.25 Freundlich b vs pH 1 d reaction 1.00

b 0.75

0.50 Freundlich Freundlich Pb Zn Ni 0.25 Cu Cd Model (eq. 4) Modified model (eq. 6) 0.00 3 5 7 pH

Fig. 15. Measured 1-day Freundlich b parameter values for all five heavy metals. The solid and dashed lines were calculated using equations (4) and (6), respectively.

LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils 19 1.25 Freundlich b vs pH (7 d reaction) 1.00

b 0.75

0.50 Freundlich Freundlich Pb Zn Ni 0.25 Cu Cd Model (eq. 4) Modified model (eq. 7) 0.00 3 5 7 pH

Fig. 16. Measured 7-day Freundlich b parameter values for all five heavy metals. The solid and dashed lines were calculated using equations (4) and (7), respectively.

20 LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils SUMMARY AND CONCLUSIONS LITERATURE CITED The retention of five heavy elements by 10 soils from Agbenin, J.O., Olojo, L.A., 2004. Competitive adsorption 10 soil orders was quantified to determine the effects of of copper and zinc by a Bt horizon of a savanna soil properties on the magnitude of soil retention in the alfisol as affected by pH and selective removal of different soils. We also investigated the influence of time hydrous oxides and organic matter. Geoderma of reaction on sorption for all soils and heavy metals. A 119, 257–265. major finding of this study is that adsorption isotherms Arias, M., Pérez-Novo, C., López, E., Soto, B., 2006. for all heavy elements and soils were nonlinear. Moreover, Competitive adsorption and desorption of copper soil properties affecting sorption were pH, CEC, organic and zinc in acid soils. Geoderma 133, 151–159. matter, clay content and the presence of carbonates. Aringhieri, R., P. Carrai, and G. Petruzzelli. Kinetics of Cu2+ Additional findings are: and Cd2+ adsorption by an Italian soil. Soil Sci. 139:197–204. 1. Soils with high organic matter and soils with high CEC and pH from the presence of carbonates Atanassova, I. 1999. Competitive effect of copper, zinc, cadmium and nickel on ion adsorption and exhibited strong sorption for all five heavy metals. desorption by soil clays. Water Air & Soil Poll. 113: Sandy soils having low CEC showed lowest 115–125. sorption for all metals. Barrow, N. J., J. Gerth and G. W. Brümmer. 1989. Reaction- 2. For all 10 soils used in this study, adsorption of kinetics of the adsorption and desorption of nickel, heavy elements followed the order Pb > Cu > Cd > zinc and cadmium by goethite. II. Modeling the Zn > Ni. In the presence of carbonates, adsorption extent and rate of reaction. J. Soil Sci. 40 (2): 437- followed the order Pb > Cu > Zn > Cd > Ni. 450. 3. The influence of time of reaction in increased Bradl, H.B. 2004. Adsorption of heavy metal ions on soils and soil constituents. Journal of Colloid and sorption varied among soils and heavy metals. Interface Science, 277: 1-18. 4. A modified regression equation was suitable to Buchter, B., B. Davidoff, M. C. Amacher, C. Hinz, I. K. Iskandar, predict the Freundlich parameter b vs. pH for a and H. M. Selim. 1989. Correlation of Freundlich 1-day reaction time. The modified equations were Kd and n retention parameters with soils and similar to that proposed by Buchter (1989) with elements. Soil Sci. 148:370-379. significantly different intercept. Dang Y.P., Dalal R.C. D. G. Edwards D.G., and K. G. Tiller. 1994. 5. With the exception of Cu, the Freundlich Kinetics of zinc desorption from vertisols. Soil Sci. Soc. Am. J. 58: 1392-1399. parameter b did not change significantly with time. USEPA, 1993. 40 CFR-Part 257 and 503, Standards for the 6. This finding, that b is time invariant, has a Disposal of Sewage Sludge; Final Rule. Fed. Regist. significant implication since it simplifies predictive 58:9248–9415. US EPA, Washington, DC, USA. capabilities of affinity for sorption of heavy metals http://www.ecfr.gov/cgi-bin/text-idx?tpl=/ecfrbrowse/ with time. Title40/40cfr503_main_02.tpl USEPA. 1994a. A plain English guide to EPA Part 503 ACKNOWLEDGEMENTS Biosolids Rule EPA-832-R-93-003. USEPA Office of Wastewater Management, Washington, DC. This work was funded in part by a grant from USDA- http://water.epa.gov/scitech/wastetech/biosolids/503pe_ ARS, Tempe, Texas Agreement 59-6206-2-058 (2013- index.cfm 2014). The author expresses his appreciation to several USEPA, 1994b. A Guide to the Biosolids Risk Assessments students and colleagues who contributed to this bulletin. for the EPA Part 503 Rule. EPA 832-B-93-05. USEPA Dr. Dustin Harrell provided the corn and rice Zn response Office of Wastewater Management, Washington, photos of the front cover, and Scott Senseman from Texas DC. A&M provided several the soils used in this study. Special http://water.epa.gov/polwaste/wastewater/treatment/ thanks go to my graduate students Nazanin Akramai, biosolids/upload/2002_06_28_mtb_biosolids_ Tamer Elbana and April Newman. Special thanks also goes sludge.pdf to Drs. Virginia Jin and Jeff Arnold, USDA-ARS, for their USEPA.1995. Land application of sewage sludge and help during the course of this study. domestic seepage: Process design manual. EPA- 625-R-95-001. USEPA, Washington, DC. http://nepis.epa.gov/Adobe/PDF/30004O9U.pdf

LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils 21 USEPA. 1999. Understanding variation in partition D. Fernández-Calviño, and M. Arias-Estévez. coefficient, Kd, values. Report EPA 402-R-99-004A. 2011a. Zinc adsorption in acid soils Influence of Elbana, Tamer A and H. M. Selim. 2010. Cadmium Transport phosphate. Geoderma 162:358–364. in alkaline acidic soils: Miscible displacement Saha, U.K., Taniguchi, S., Sakurai, K., 2002. Simultaneous experiments. Soil Science Society of America adsorption of cadmium, zinc,and lead on Journal 74: 1956–1966. hydroxyaluminium– and hydroxyaluminosilicate– Elbana, T. A. and H M. Selim. 2011. Copper Mobility in montmorillonite complexes. Soil Science Society of Acidic and Alkaline Soils: Miscible Displacement America Journal 66, 117–128. Experiments. Soil Science Society of America Scheckel, K. G. and D. L. Sparks. 2001. Dissolution kinetics Journal 75:2101–2110. of nickel surface precipitates on clay mineral and Florido, A., C. Valderrama, J. A. Arevalo, I. Casas, M. Martinez, oxide surfaces. Soil Sci. Soc. Am. J. 65:685-694. and N. Miralles. 2010. Application of two sites Selim, H. M. 2015. Chemical Transport and Fate in Soils: non-equilibrium sorption model for the removal Principals and Applications. CRC/Taylor and of Cu(II) onto grape stalk wastes in a fixed-bed Francis, Boca Raton, FL (352 p). column. Chem. Eng. J., 156: 298–304. http://www.crcpress.com/product/ Fontes, M. 2012. Behavior of Heavy Metals in Soils: isbn/9781466557949 Individual and Multiple Competitive Adsorption. Selim, H. M. 2014. On the nonlinearity of sorption of solutes Chapter 3 in Selim (ed) “Competitive Sorption and in soil. Soil Sci. 179:237-241. Transport of Trace Elements in Soils and Geological Media”, CRC, pages (77-117). Selim, H. M. 2013. Transport and Retention of Heavy Metal in Soils: Competitive Sorption. Adv. Agron. 119: Giles, C.H., D’Silva, A.P. and Easton, I.AJ. 1974. A general 275-308. classification of the solute adsorption isotherms II. J. Colloid Interface Sci., 47: 766-778. Selim, H. M., B. Buchter, C. Hinz and L. Ma. 1992. Modeling the Transport and Retention of Cadmium in Soils: Hinz, C., and H.M. Selim. 1994. Transport of Zinc and Mulltireaction and multicomponent approaches. Cadmium in Soils - Experimental-Evidence and Soil Sci. Soc. Am. J. 56:1004-1015. Modeling Approaches. Soil Sci. Soc. Am. J. 58:1316- 1327. Selim, H. M. and L. Ma. 2001. Modeling nonlinear kinetic behavior of copper adsorption-desorption in soil. Hooda, P.S. and B.J. Alloway. 1998. Cadmium and lead Soil Sci. Soc. Am. Spec. Publ. 56:189-212. sorption behaviour of selected English and Indian soils. Geoderma, 84:121-134 Sparks, D. L. 2003. Environmental Soil Chemistry. Elsevier, NY. Kabata-Pendias, A. and W. Sadurski. 2007. Trace Elements in Soils and Plants. CRC, Boca Ratopn, FL. Strawn, D.G. and Sparks, D.L., 2000. Effects of soil organic matter on the kinetics and mechanisms of Pb(II) Krishnamurti, G. S. R. and R. Naidu. 2003. Solid-solution sorption and desorption in soils. Soil Sci. Soc. Am. equilibrium of cadmium in soils. Geoderma J. 64:144-156. 113:17-30. Tiller, K. G., V. K. Nayyar, and P. M. Clayton. 1984. Specific and Langmuir, I. 1918. The adsorption of gases on plane nonspecific sorption of cadmium by soils clays as surfaces of glass, mica and platinum. J. Am. Chem influenced by zinc and calcium. Aust. J. Soil Sci. Soc. 40:1361-1402. 17:17-28. Liao, Lixia and H. M. Selim. 2010. Reactivity of nickel in soils: Voegelin, A and R. Kretzschmar. 2005. Formation and Evidence of retention kinetics. J. Environ. Qual. dissolution of single and mixed Zn and Ni 39:1290–1297. precipitates in soil: Evidence from column Lopez-Periago, J.E., M. Arias-Estevez, J.C. Novoa-Munoz, D. experiments and extended X-ray absorption fine Fernandez-Calvino, B. Soto, C. Perez-Novo, and J. structure spectroscopy. Environ. Sci. Technol. 39: Simal-Gandara. 2008. Copper retention kinetics in 5311-5318. acid soils. Soil Sci. Soc. Am. J. 72:63–72. Voegelin, A., V. M. Vulava, and R. Kretzschmar. 2001. Martínez-Villegas, N., L.Ma. Flores-Vélez, and O. Domínguez, Reaction-based model describing competitive 2004. Sorption of lead in soil as a function of pH: sorption and transport of Cd, Zn, and Ni in an a study case in México. Chemosphere 57, 1537– acidic soil. Environ. Sci. Technol. 35:1651-1657. 1542. Zhao, K. and H. M. Selim. 2010. Adsorption-Desorption Mesquita, M.E., Vieira e Silva, J.M., 1996. Zinc adsorption by Kinetics of Zn in soils: Influence of phosphate. Soil a calcareous soil. Copper interaction. Geoderma Sci. 2010:175: 145-153. 69, 137–146.

Pérez-Novo, C., A. Bermúdez-Couso, E. López-Periago,

22 LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils Bioavailability of Micronutrients and Other Trace Elements in Soils

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H. Magdi Selim School of Plant, Environmental and Soil Sciences

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William B. Richardson, LSU Vice President for Agriculture Louisiana State University Agricultural Center Louisiana Agricultural Experiment Station Louisiana Cooperative Extension Service LSU College of Agriculture

Research Bulletin #894 (Online only) 7/16

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24 LSU AgCenter Research Bulletin 894 - Bioavailability of Micronutrients and Other Trace Elements in Soils